1. Field of the Invention
This invention relates to fuel injection systems for internal combustion engines and more particularly to a computer for controlling the time and quantity of injection of fuel to engine cylinders in synchronism with operation of the engine. This invention may be used in a system such as that described in my U.S. patent application, Ser. No. 629,421, entitled "Fuel Injection System" filed concurrently herewith on Nov. 6, 1975.
2. Prior Art
A fuel injection system for an internal combustion engine replaces a conventional carburetor with a number of fuel injectors. The injectors are connected to a pressurized fuel conduit and may be electrically energized to provide fuel from the conduit to their associated cylinders. The amount of fuel provided is a function of the pressure in the conduit and is proportional to the length of time for which the injector is actuated by the duration of an electrical control pulse.
In some early fuel injection systems, control pulses were provided sequentially to each of the injectors. Fully sequential systems have insufficient cycle time to perform the fuel metering function properly resulting in poor fuel economy and high exhaust emissions.
All known prior art fuel injection systems are limited by problems of: slow reaction time to changes in engine operating conditions, or insufficient cycle time for proper metering, or both problems. Both problems result from the single channel configuration of the fuel injection system. Single channel configuration requires the individual injectors to share available engine cycle time. For example, if engine cycle time is 20 milliseconds and four groups of injectors, each group having two injectors, are used, each group of injectors has less than 5 milliseconds of engine cycle time, that is, clearly less than 50% of cycle time. Later, control pulses were provided to all of the injectors simultaneously. It was found that simultaneous injection limits engine performance, that is, the speed of response to the engine to changes in operating parameters. For example, if the accelerator is suddenly depressed, the increased fuel charge called for by this action may not reach the engine for one or two engine cycles. In recent years, interest in fuel injection systems has centered about the prospect of minimizing the generation of pollutants in exhaust emission by metering the fuel provided to the engine more carefully than a carburetor. As a result, hybrid systems have been developed which are partially sequential, having the advantages and disadvantages of both systems.